Relay optical system

ABSTRACT

The relay optical system comprises, in order from the intermediate image position I toward the the exit pupil EXP side, a first unit G 1  having a negative refracting power and a second unit G 2  having a positive refracting power, wherein the distance from the rearmost surface of the second unit to the exit pupil position is at least 30 mm. The relay optical system allows a photographing apparatus to be mounted on a microscope without the microscope and the photographing apparatus excluding each other from their predetermined positions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 09/878,183, filed Jun. 12, 2001, now U.S. Pat. no. 6,496,308, thespecification and drawings of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a relay optical system used forphotographing, with an electronic image-pickup camera or the like, animage formed by an objective lens.

2. Description of Related Art

As measures to record an image formed by an objective lens of amicroscope, there are the photography using a silver halide camera andthe photography using a TV camera. According to the photography with asilver halide camera, a sample image is recorded on a film.

On the other hand, the photography with a TV camera is disclosed inJapanese Patent Application Preliminary Publication (KOKAI) No. Hei6-331903, where a TV camera connecting tube that comprises an ocularobservation barrel, an adapter, an attachment for a TV camera, and aphotographing section of the TV camera is shown. Although an imagesensor is not particularly described in this document, a solid-stateimage sensor (CCD), for example, may be used.

Conventionally, the number of pixels of a solid-state image sensor isroughly determined in accordance with the number of scanning lines of aTV monitor. For example, an image sensor with 512×512 pixels or 640×512pixels is used for the standard format (NTSC), and an image sensor with1024×768 pixels is used for the high-definition type.

As described above, according to the conventional photography, a sampleimage is recorded on a film, while, in recent years, digital camerasusing, as the recording medium, solid state image sensors have appearedin the market, to be popularized. The digital camera is characterized inits large number of pixels for the area of the solid-state image sensor.In early years, hundreds of thousands of pixels would be provided forthe ⅓-inch type, while, in recent years, one or two millions of pixelsor more are provided for the ⅔-inch or ½-inch type.

However, the digital camera is constructed to have a photographing lensfixed to the camera body and thus the entrance pupil position is placedinside the photographing lens or the camera body. Therefore, if a personwould try to use the camera in combination with a microscope forphotographing a sample image, he has to position the body of the digitalcamera close to the lens barrel of the microscope so as to make the exitpupil position (or a position conjugate with the exit pupil position) ofthe microscope coincide with the entrance pupil position of the digitalcamera. As a result, the microscope and the digital camera would excludeeach other from their predetermined positions, which is a problem.

It is noted that each of Japanese Patent Application PreliminaryPublication (KOKAI) No. Hei 2-222914, Japanese Patent ApplicationPreliminary Publication (KOKAI) No. Hei 9-54258, Japanese PatentApplication Preliminary Publication (KOKAI) No. Hei 9-133875 andJapanese Patent Application Preliminary Publication (KOKAI) No. Hei10-39235 discloses an optical system used for observation of an image(intermediate image) formed by an objective lens. However, such anoptical system is directed for observation via human eyes and thus isdifficult of use as a relay optical system for a photographingapparatus.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a relay optical systemthat allows a photographing apparatus to be mounted on a microscopewithout the microscope and the photographing apparatus excluding eachother from their predetermined positions.

A relay optical system according to the present invention comprises, inorder from the intermediate image position toward the exit pupil side, afirst unit having a negative refracting power and a second unit having apositive refracting power and is characterized in that a distance fromthe rearmost lens surface of the second lens unit to the exit pupilposition is at least 30 mm.

Also, it is characterized in comprising at least four lenses.

Also, it is characterized in that the distance from the rearmost lenssurface of the second unit to the exit pupil position is in a range from30 mm to 160 mm.

Also, it is characterized in that the distance from the rearmost lenssurface of the second unit to the exit pupil position is in a range from30 mm to 90 mm.

This and other objects as well as features and advantages of the presentinvention will become apparent from the following detailed descriptionof the preferred embodiments when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view to show the schematic configuration of a microscope inwhich the relay optical system according to the present invention isused.

FIG. 2 is a sectional view of the relay optical system according to thefirst embodiment of the present invention taken along the optical axis.

FIGS. 3A-3C are aberration diagrams regarding the first embodiment.

FIG. 4 is a sectional view of the relay optical system according to thesecond embodiment of the present invention taken along the optical axis.

FIG. 5 is a sectional view of the relay optical system according to thethird embodiment of the present invention taken along the optical axis.

FIG. 6 is a sectional view of the relay optical system according to thefourth embodiment of the present invention taken along the optical axis.

FIGS. 7A-7C are aberration diagrams regarding the fourth embodiment.

FIG. 8 is a sectional view of the relay optical system according to thefifth embodiment of the present invention taken along the optical axis.

FIG. 9 is a sectional view of the relay optical system according to thesixth embodiment of the present invention taken along the optical axis.

FIGS. 10A-10C are aberration diagrams regarding the sixth embodiment.

FIG. 11 is a sectional view of the relay optical system according to theseventh embodiment of the present invention taken along the opticalaxis.

FIG. 12 is a sectional view of the relay optical system according to theeighth embodiment of the present invention taken along the optical axis.

FIGS. 13A-13C are aberration diagrams regarding the eighth embodiment.

FIG. 14 is a sectional view of the relay optical system according to theninth embodiment of the present invention taken along the optical axis.

FIG. 15 is a sectional view of the relay optical system according to thetenth embodiment of the present invention taken along the optical axis.

FIG. 16 is a sectional view of the relay optical system according to theeleventh embodiment of the present invention taken along the opticalaxis.

FIGS. 17A-17C are aberration diagrams regarding the eleventh embodiment.

FIG. 18 is a sectional view of the relay optical system according to thetwelfth embodiment of the present invention taken along the opticalaxis.

FIG. 19 is a sectional view of the relay optical system according to thethirteenth embodiment of the present invention taken along the opticalaxis.

FIGS. 20A-20C are aberration diagrams regarding the thirteenthembodiment.

FIG. 21 is a sectional view of the relay optical system according to thefourteenth embodiment of the present invention taken along the opticalaxis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Description will be made of the modes for carrying out the presentinvention based on the embodiments presented with the drawings.

A relay optical system according to the present invention comprises, inorder from the intermediate image position toward the exit side, a firstunit having a negative refracting power and a second unit having apositive refracting power. A distance d_(EXP) from the rearmost lenssurface of the second unit to the exit pupil position is at least 30 mm.

Also, the constituent lenses of the relay optical system include atleast four lenses. In this configuration, it is preferred that thedistance d_(EXP) from the rearmost lens surface of the second unit tothe exit pupil position is in a range from 30 mm to 160 mm.

In reference to FIG. 1, which shows the situation where the relayoptical system of the present invention is used with a microscope, thedistance d_(EXP) is equivalent to the distance from the most digitalcamera-side lens surface of the relay optical system 3 to the positionof the entrance pupil 8 of the digital camera 6. Thus, if the distanced_(EXP) is shorter than the lower limit value of 30 mm, an attempt tomake the exit pupil position of the relay optical system 3 coincide withthe entrance pupil position of the photographing lens 6A of the digitalcamera 6 would fail, because the space between the observation barrel 2and the digital camera 6 becomes so small that the observation barrel 2and the digital camera 6 would exclude each other from theirpredetermined positions. In addition, if a digital camera having aphotographing lens with a long focal length is coupled, a problem occursin that rays corresponding to the periphery of the image are eclipsed,because the entrance pupil of such a type of digital camera ispositioned close to the image sensor thereof.

If the distance d_(EXP) exceeds the upper limit value of 160 mm, theobservation barrel 2 and the digital camera 6 are so distant from eachother as to degrade the stability, and thus photographing of a sharpsample image is obstructed. In addition, it is made difficult toincrease the magnification of the relay optical system 3 to be greaterthan 3×, and accordingly, a problem occurs in that a full-angle image,which the photographing lens 6A is inherently capable of providing,cannot be photographed without eclipse.

Also, in the above-mentioned configuration, it is desirable that therelay optical system of the present invention satisfies the followingcondition (1):0.3≦L/f≦1.25  (1)where L is a total length of the relay optical system defined by thedistance from a lens surface on which light is first incident to a lenssurface from which the light is emergent lastly, and f is a focal lengthof the relay optical system.

Regarding Condition (1), a value of L/f smaller than the lower limitvalue, 0.3 means that the number of lenses is small, which makes itdifficult to compensate aberrations of the relay optical system in goodcondition. A value exceeding the upper limit value, 1.25 makes itdifficult to secure the necessary distance to the exit pupil position.In this regard, it is much desirable to satisfy the following condition(1′):0.4≦L/f≦1.25  (1′)

Also, it is desirable that the following conditions (2)-(4) aresatisfied in place of or in addition to Condition (1).−12≦f ₁ /f≦−0.2  (2)0.45≦f ₂ /f≦1.5  (3)0.9≦d _(EXP) /f≦2.5  (4)where f₁ is a focal length of the first unit, f₂ is a focal length ofthe second unit, and d_(EXP) is the distance from the rearmost lenssurface of the second unit to the exit pupil position.

Regarding Condition (2), a value of f₁/f smaller than the lower limitvalue, −12 means that the refracting power of the first unit is small,and accordingly Petzval sum cannot be small, or the curvature of fieldcannot be sufficiently compensated. A value exceeding the upper limitvalue, −0.2 means that the refracting power of the first unit is large,which makes it difficult to compensate aberrations of the entire relayoptical system in good condition and, in addition, necessitates a largeouter diameter of lenses of the second unit.

Regarding Condition (3), a value of f₂/f smaller than the lower limitvalue, 0.45 means that the refracting power of the second unit is largeand that the refracting power of the first unit also is large,accordingly. In this case, since amount of aberrations caused by each ofthe first unit and the second unit becomes large, the sphericalaberration and the curvature of field cannot cancel out in the firstunit and the second unit, and thus it is difficult to achievewell-balanced compensation of aberrations. Also, a value exceeding theupper limit value, 1.5 means that the refracting power of the secondunit is small and that the refracting power of the first unit also issmall, accordingly. As a result, shortage of the negative refractingpower makes it difficult to achieve effective compensation of thecurvature of field.

Regarding Condition (4), if a value of d_(EXP)/f is smaller than thelower limit value, 0.9 or larger than the upper limit value, 2.5, it isdifficult to set a photographing apparatus, where it is used incombination with a microscope, in an appropriate position in a goodbalance. It is noted that the value of d_(EXP) is measured under thecondition where the entrance pupil of the relay optical system ispositioned at the substantially infinite distance.

The relay optical system according to the first mode of the presentinvention is composed of four lenses. In the first configuration basedon this mode, the first unit with a negative refracting power iscomposed of a cemented lens, and the second unit with a positiverefracting power is composed of two positive lenses. Also, in the secondconfiguration based on this mode, the first unit with a negativerefracting power is composed of a negative meniscus lens directing aconvex surface thereof toward the intermediate image side, and thesecond unit with a positive refracting power is composed of a cementedlens and a positive lens. Also, in the third configuration based on thismode, the first unit with a negative refracting power is composed of abiconcave lens, and the second unit with a positive refracting power iscomposed of a cemented lens and a positive lens.

In the first, second or third configuration, Condition (1) or Condition(1′) set fourth above is satisfied.

Also, in the first, second or third configuration, it is desirable thatthe following conditions (2′), (3) and (4′) are satisfied:−12≦f ₁ /f≦−0.5  (2′)0.45≦f ₂ /f≦1.5  (3)0.9≦d _(EXP) /f≦1.5  (4′)

Significance of the upper and lower limit values of Condition (3) isexplained above. Significance of the upper and lower limit values ofConditions (2′), (4′) is the same as explained above regardingConditions (2), (4). In the case where the relay optical system iscomposed of four lenses as in the first, second or third configuration,it is desirable that f₁/f falls within the range determined by Condition(2′), that f₂/f falls within the range determined by Condition (3), andthat d_(EXP)/f falls within the range determined by Condition (4′).

FIG. 1 shows a microscope in which the relay optical system according tothe present invention is used. In the drawing, the reference numeral 1represents a microscope body, the reference numeral 2 represents anobservation barrel, the reference numeral 3 represents a relay opticalsystem, the reference numeral 4 represents a first holder member whichholds the relay optical system 3, the reference numeral 5 represents asecond holder member, the reference numeral 6 represents a digitalcamera (electronic image-pickup camera), and the reference numeral 8represents the entrance pupil of a built-in photographing lens 6A. Also,the reference numeral 11 represents a revolver, the reference numeral 12represents an objective lens, and the reference numeral 13 represents astage on which a sample S is placed.

The lower section of the observation barrel 2 is fixed on the topsurface of the microscope body 1. An observation path 2A for ocularobservation of an image of the sample S and a photographing path 2B forphotographing with the digital camera 6 are provided inside theobservation barrel 2. An eyepiece 9 is disposed in the observation path2A to allow an observer ocular observation. Switching between theobservation path 2A and the photographing path 2B is made by insertionor removal of a prism 10 in or out of the path via manipulation of aswitching lever, not shown. The reference symbol I represents anintermediate image, which is formed outside the observation barrel 2.

On the upper side of the observation barrel 2, the first holder member 4is provided. The first holder member 4 is connected, via the lower end4A thereof, with the observation barrel 2. The first holder member 4 hasa hollow cylindrical shape so that the relay optical system 3 isarranged inside.

The relay optical system 3 is held inside the first holder member 4 inthe vicinity of the upper end 4B thereof in such a manner that theposition of the sample image I coincides with the front-side focal pointof the relay optical system 3 or the vicinity thereof. Accordingly, raysfrom every point on the sample image I enter the digital camera afterbeing converted by the relay optical system 3 into a beam of parallelrays or a beam of substantially parallel rays. Also, the exit pupil (ora conjugate point thereto) of the microscope and the entrance pupil 8 ofthe digital camera 6 are made to coincide or substantially coincide bythe relay optical system 3.

On the upper side of the first holder member 4, the second holder member5 is mounted in such a manner that the upper end 4B of the first holdermember 4 and the lower end 5A of the second holder member 5 areconnected together. The second holder member 5 has a hollow cylindricalshape similar to the first holder member 4, but no lens is held inside.

On the upper side of the second holder member 5, the digital camera 6 isattached. An adapter 7 for connection with the second holder member 5 isprovided outside the rim of the photographing lens 6A. The end of theadapter 7 and the upper end 5B of the second holder member 5 areconnected together. If structure allows, the digital camera 6 may bedirectly connected with the holder member 5.

For connection between members, e.g. connection between the microscopebody 1 and the observation barrel 2, and connection between the secondholder member 5 and the adapter 7, a conventional mechanism such as thescrew mechanism or the round dovetail mechanism is appropriatelyselected.

In the case where the relay optical system 3 is composed of four lenses,it is desirable that the following condition (5) is satisfied:30 mm≦d _(EXP)≦90 mm  (5)

Arranging d_(EXP) to be equal to or smaller than 90 mm allows thefull-angle image, which the photographing lens 6A is inherently capableof providing, to be photographed without eclipse.

Since the relay optical system 3 according to the present inventionsatisfies Condition (5), the digital camera 6 and the observation barrel2 can be sufficiently spaced away from each other under stablecondition. Therefore, photographing of a sample image can be performedunder the stable condition without the digital camera 6 and theobservation barrel 2 excluding each other from their predeterminedpositions. Also, since the optical system is adapted to the opticalcharacteristics of the photographing lens 6A of the digital camera, agood sample image without eclipse can be obtained over a fullphotographing angular range.

Also, it is much preferable that the relay optical system 3 satisfiesthe following condition (6) in place of Condition (5):60 mm≦d _(EXP)≦80 mm  (6)

The relay optical system according to the second mode of the presentinvention is composed of five lenses. In the fourth configuration basedon this mode, the first unit with a negative refracting power iscomposed of a singlet lens, and the second unit with a positiverefracting power is composed of, in order from the intermediate imageposition toward the exit side, a cemented lens and two positive lenses.Also, in the fifth configuration based on this mode, the first unit witha negative refracting power is composed of a singlet lens as in thefourth configuration, and the second unit with a positive refractingpower is composed of, in order from the intermediate position toward theexit side, a positive lens, a cemented lens and a positive lens. Also,in the sixth configuration based on this mode, the first unit with anegative refracting power is composed of a negative cemented lens, andthe second unit with a positive refracting power is composed of, inorder from the intermediate image position to the exit side, a cementedlens and a positive lens.

In the fourth, fifth or sixth configuration, Condition (1) or Condition(1′) set fourth above is satisfied.

Also, in the fourth, fifth or sixth configuration, it is desirable thatthe following conditions (2″), (3′) and (4″) are satisfied:−2≦f ₁ /f≦−0.2  (2″)0.45≦f ₂ /f≦1.2  (3′)1≦d _(EXP) /f≦2.5  (4″)

Significance of the upper and lower limit values of Conditions (2″),(3′), (4″) is the same as explained above regarding Conditions (2), (3),(4). In the case where the relay optical system is composed of fivelenses as in the fourth, fifth or sixth configuration, it is desirablethat f₁/f falls within the range determined by Condition (2″), that f₂/ffalls within the range determined by Condition (3′), and that d_(EXP)/ffalls within the range determined by Condition (4″).

In the case where the relay optical system 3 is composed of five lenses,it is desirable that the following condition (7) is satisfied:60 mm≦d _(EXP)≦160 mm  (7)

Since the relay optical system 3 according to the present inventionsatisfies Condition (7), the digital camera 6 and the observation barrel2 can be sufficiently spaced away from each other under stablecondition. Therefore, photographing of a sample image can be performedunder the stable condition without the digital camera 6 and theobservation barrel 2 excluding each other from their predeterminedpositions. Also, since the optical system is adapted to the opticalcharacteristics of the photographing lens 6A of the digital camera, agood sample image without eclipse can be obtained over a fullphotographing angular range.

Also, it is much desirable that the relay optical system 3 satisfies thefollowing condition (8) in place of Condition (7)90 mm≦d _(EXP)≦160 mm  (8)

Also, it is still much desirable that the relay optical system 3satisfies the following condition (9) in place of Condition (7):90 mm≦d _(EXP)≦130 mm  (9)

In a microscope with which the relay optical system of the presentinvention is used, the digital camera 6 is connected with the microscopevia the first holder member 4, the second holder member 5 and theadapter 7, as described above. Here, the first holder member 4, thesecond holder member 5 and the adapter 7 are fabricated withconsiderable accuracy, to have dimensions as designed.

On the other hand, the fabrication accuracy of the body of the digitalcamera 6 is not so high as that of the adapter 7 or the holder member 5.Therefore, when the digital camera 6 is mounted on the adapter 7, theposition of the image formed by the photographing lens 6A in referenceto the lateral end face of the digital camera is slightly displaced fromthe designed position. As a result, even if focusing is made on thesample via the eyepiece, an in-focus image is not necessarily formed onthe image pickup surface of the digital camera 6.

Therefore, with the digital camera 6 provided with a display device formonitoring, e.g. a liquid crystal display surface, the observer shouldperform focus adjustment while viewing an image displayed on the liquidcrystal display surface. However, the long distance from the liquidcrystal display surface to the focusing knob of the microscope bodymakes it difficult to perform focus adjustment.

In such a case, use of the auto-focus function of the digital camera 6facilitates accurate confocal adjustment of the digital camera 6 inreference to the image by the eyepiece. This method is especiallyadvantageous in the following situation.

Focusing operation is difficult in the case of photographing using alow-magnification objective lens. Specifically, it is considerablydifficult to perform focus adjustment by operating the focusing knob ofthe microscope body as monitoring the liquid crystal display surface.However, if confocality with the image via the eyepiece is detected bythe above-described method, simple focus adjustment via the eyepiecesimultaneously achieves focus adjustment for the photographed image.Moreover, since the eyepiece is positioned close to the focusing knob ofthe microscope body, focusing can be performed easily. In this way,operability is improved. In addition, since the eyepiece provides animage with better quality than the liquid crystal display surface does,more accurate focusing can be achieved even by ocular observation.

When the photographing lens 6A is moved for focus adjustment, the pupilposition (entrance pupil position) of the photographing lens 6A isshifted from the pupil position (exit pupil position) projected by therelay optical system 3. However, the amount of shift is very little andthus would not cause a considerable problem.

Embodiment 1

FIG. 2 shows the first embodiment of the relay optical system accordingto the present invention. This embodiment is directed to the relayoptical system of the first configuration, where the first unit G1 witha negative refracting power is composed of a cemented lens having abiconcave lens and a biconvex lens arranged in order from theintermediate image side to the exit pupil EXP side, and the second unitG2 with a positive refracting power is composed of two biconvex lenses.

All the surfaces of the biconcave lens and the biconvex lens of thefirst unit G1 with a negative refracting power have the same absolutevalue of radius of curvature. The two biconvex lenses of the second unitG2 with a positive refracting power differ from each other in shape andare arranged so that the surfaces with the smaller absolute values ofradius of curvature of the respective lenses face one another.

The numerical data of this embodiment are shown below. In the data, thecolumn R shows the radius of curvature of each lens surface, the columnT shows the thickness of each lens or airspace between lenses, which isrepresented by d₁, d₂, d₃ . . . in the drawing, the column nd shows therefractive index of each lens for d-line rays, and the column vd showsthe Abbe's number of each lens. This manner is commonly used in thesubsequent embodiments also. “INF” appearing in the line of surfacenumber 1 means that it is the intermediate image position, and “INF”appearing in the line of surface number 9 means that it is the exitpupil EXP position.

Surface No. (r) R T nd νd 1 INF 11.1142 2 −30.393 4.2000 1.84666 23.78 330.393 10.9000 1.58913 61.14 4 −30.393 1.0000 5 145.200 6.1000 1.4874970.23 6 −45.256 1.0000 7 34.698 8.4000 1.48749 70.23 8 −87.355 35.9300 9INF

Regarding the spherical aberration, astigmatism and distortion of thisembodiment, aberration diagrams are shown in FIGS. 3A-3C.

Embodiment 2

FIG. 4 shows the second embodiment of the relay optical system accordingto the present invention. In this embodiment also, as in Embodiment 1,the first unit G1 with a negative refracting power is composed of acemented lens having a biconcave lens and a biconvex lens arranged inorder from the intermediate image side, and the second unit G2 with apositive refracting power is composed of two biconvex lenses.

The surfaces of the biconcave lens of the first unit G1 with a negativerefracting power have the same absolute value of radius of curvature.The two biconvex lenses of the second unit G2 with a positive refractingpower have an identical shape and are arranged so that the surfaces withthe smaller absolute value of radius of curvature of the respectivelenses face one another.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 7.1015 2 −19.467 3.0000 1.84666 23.78 319.467 11.4000 1.58913 61.14 4 −24.763 1.0000 5 68.589 6.0000 1.4874970.23 6 −36.368 1.0000 7 36.368 6.0000 1.48749 70.23 8 −68.589 35.5870 9INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 1 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 3

FIG. 5 shows the third embodiment of the relay optical system accordingto the present invention. In this embodiment also, as in Embodiment 1,the first unit G1 with a negative refracting power is composed of acemented lens having a biconcave lens and a biconvex lens arranged inorder from the intermediate image side, and the second unit G2 with apositive refracting power comprises biconvex lenses.

The surfaces of the biconvex lens of the first unit G1 with a negativerefracting power have the same absolute value of radius of curvature.The two biconvex lenses of the second unit G2 with a positive refractingpower differ from each other in shape and are arranged so that thesurfaces with the smaller absolute values of radius of curvature of therespective lenses face one another.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 12.2390 2 −45.876 5.1000 1.84666 23.78 332.066 11.0000 1.58913 61.14 4 −32.066 1.0000 5 97.713 5.9000 1.4874970.23 6 −71.183 1.0000 7 29.992 9.2000 1.48749 70.23 8 −168.989 31.05299 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 1 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 4

FIG. 6 shows the fourth embodiment of the relay optical system accordingto the present invention. This embodiment is directed to the relayoptical system of the second configuration, where the first unit G1 witha negative refracting power is composed of a negative meniscus lensdirecting a convex surface thereof toward the intermediate image side,and the second unit G2 with a positive refracting power is composed of,in order from the intermediate image side, a cemented lens having apositive lens and a negative lens arranged in this order, and a positivelens.

The cemented lens of the second unit G2 with a positive refracting poweris constructed of a biconvex lens and a negative meniscus lens directinga concave surface thereof toward the intermediate image side and has apositive refracting power as a whole. The positive lens of the secondunit G2 with a positive refracting power is a biconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 11.8417 2 32.1231 4.0000 1.69895 30.13 320.1111 3.0925 4 55.7176 10.6575 1.51633 64.14 5 −16.7356 3.8973 1.7407727.79 6 −43.3920 1.0000 7 55.3289 9.0162 1.69100 54.82 8 −39.755730.1409 9 INF

Regarding the spherical aberration, astigmatism and distortion of thisembodiment, aberration diagrams are shown in FIGS. 7A-7C.

Embodiment 5

FIG. 8 shows the fifth embodiment of the relay optical system accordingto the present invention. In this embodiment also, as in Embodiment 4,the first unit G1 with a negative refracting power is composed of anegative meniscus lens directing a convex surface thereof toward theintermediate image side, and the second unit G2 with a positiverefracting power is composed of, in order from the intermediate imageside, a cemented lens having a positive lens and a negative lensarranged in this order, and a positive lens.

The cemented lens of the second unit G2 with a positive refracting poweris constructed of a biconvex lens and a negative meniscus lens directinga concave surface thereof toward the intermediate image side and has apositive refracting power as a whole. The positive lens of the secondunit G2 with a positive refracting power is a positive meniscus lensdirecting a concave surface thereof toward the intermediate image side.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 35.5987 2 89.0738 4.0000 1.69895 30.13 327.0854 5.2995 4 38.2208 11.0000 1.51633 64.14 5 −27.3767 4.0000 1.7407727.79 6 −35.9861 1.8190 7 −110.2847 6.0000 1.69100 54.82 8 −61.045065.6468 9 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 4 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 6

FIG. 9 shows the sixth embodiment of the relay optical system accordingto the present invention. This embodiment is directed to the relayoptical system of the third configuration, where the first unit G1 witha negative refracting power is composed of a biconcave lens, and thesecond unit G2 with a positive refracting power is composed of, in orderfrom the intermediate image side, a cemented lens having a positive lensand a negative lens arranged in this order, and a positive lens.

The cemented lens of the second unit G2 with a positive refracting poweris constructed of a biconvex lens and a negative meniscus lens directinga concave surface thereof toward the intermediate image side and has apositive refracting power as a whole. The positive lens of the secondunit G2 with a positive refracting power is a biconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 14.6795 2 −417.2840 3.5000 1.68893 31.073 34.6376 3.6016 4 47.5064 10.9500 1.49700 81.54 5 −18.3517 3.85981.74077 27.79 6 −29.4224 0.5000 7 47.2898 6.4300 1.74100 52.64 8−157.4495 38.5181 9 INF

Regarding the spherical aberration, astigmatism and distortion of thisembodiment, aberration diagrams are shown in FIGS. 10A-10C.

Embodiment 7

FIG. 11 shows the seventh embodiment of the relay optical systemaccording to the present invention. In this embodiment also, as inEmbodiment 6, the first unit G1 with a negative refracting power iscomposed of a biconcave lens, and the second unit G2 with a positiverefracting power is composed of, in order from the intermediate imageside, a cemented lens having a positive lens and a negative lensarranged in this order, and a positive lens.

The cemented lens of the second unit G2 with a positive refracting poweris constructed of a biconvex lens and a negative meniscus lens directinga concave surface thereof toward the intermediate image side and has apositive refracting power as a whole. The positive lens of the secondunit G2 with a positive refracting power is a positive meniscus lensdirecting a convex surface thereof toward the intermediate image side.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 41.1156 2 −89.8328 7.5000 1.68893 31.073 41.3356 3.7277 4 56.6411 11.0304 1.49700 81.54 5 −31.3968 4.64421.74077 27.79 6 −33.6487 0.5000 7 59.6636 5.9477 1.74100 52.64 8146.6294 88.0016 9 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 6 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 8

FIG. 12 shows the eighth embodiment of the relay optical system 3according to the present invention. This embodiment is directed to therelay optical system of the fourth configuration, where the first unitG1 with a negative refracting power is composed of a biconcave lens, andthe second unit G2 with a positive refracting power is composed of, inorder from the intermediate image side to the exit pupil EXP side, acemented lens having a biconvex lens and a negative meniscus lensarranged in this order, a positive meniscus lens, and a biconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 16.525 2 −161.132 4.000 1.67270 32.1 359.307 3.834 4 164.121 11.500 1.51633 64.1 5 −17.261 5.000 1.67270 32.16 −70.640 0.897 7 −146.124 8.500 1.69100 54.8 8 −42.677 1.179 9 83.9109.000 1.48749 70.2 10 −70.958 60.042 11 INF

Regarding the spherical aberration, astigmatism and distortion of thisembodiment, aberration diagrams are shown in FIGS. 13A-13C.

Embodiment 9

FIG. 14 shows the ninth embodiment of the relay optical system 3according to the present invention. In this embodiment also, as inEmbodiment 8, the first unit G1 with a negative refracting power iscomposed of a biconcave lens, and the second unit G2 with a positiverefracting power is composed of, in order from the intermediate imageside to the exit pupil EXP side, a cemented lens having a biconvex lensand a negative meniscus lens arranged in this order, a positive meniscuslens, and a biconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 13.760 2 −48.961 6.322 1.67270 32.1 356.714 3.801 4 1127.439 13.001 1.51633 64.1 5 −18.977 5.650 1.74077 27.86 −51.619 0.891 7 −116.867 10.241 1.69100 54.8 8 −40.394 1.012 9 107.26710.501 1.48749 70.2 10 −74.855 90.020 11 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 8 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 10

FIG. 15 shows the tenth embodiment of the relay optical system 3according to the present invention. In this embodiment, the first unitG1 with a negative refracting power is composed of a biconcave lens, andthe second unit G2 with a positive refracting power is composed of, inorder from the intermediate image side to the exit pupil EXP side, acemented lens having a positive meniscus lens and a negative meniscuslens arranged in this order, a positive meniscus lens, and a biconvexlens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 23.944 2 −29.587 6.636 1.67270 32.1 355.474 3.800 4 −8532.319 13.001 1.51633 64.1 5 −23.530 5.651 1.6727032.1 6 −76.030 0.891 7 −116.940 10.241 1.69100 54.8 8 −42.171 0.997 9110.106 12.000 1.48749 70.2 10 −75.694 159.930 11 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 8 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 11

FIG. 16 shows the eleventh embodiment of the relay optical system 3according to the present invention. This embodiment is directed to therelay optical system of the fifth configuration, where the first unit G1with a negative refracting power is composed of a biconcave lens, andthe second unit G2 with a positive refracting power is composed of, inorder from the intermediate image side to the exit pupil EXP side, abiconvex lens, a cemented lens having a biconcave lens and a biconvexlens arranged in this order, and a biconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 13.679 2 −26.706 5.965 1.69895 30.1 374.140 1.987 4 139.326 12.000 1.48749 70.2 5 −27.722 5.356 6 −92.4058.390 1.80518 25.4 7 513.709 12.000 1.71300 53.9 8 −61.407 2.635 974.608 12.000 1.48749 70.2 10 −105.704 90.029 11 INF

Regarding the spherical aberration, astigmatism and distortion of thisembodiment, aberration diagrams are shown in FIGS. 17A-17C.

Embodiment 12

FIG. 18 shows the twelfth embodiment of the relay optical system 3according to the present invention. In this embodiment also, as inEmbodiment 11, the first unit G1 with a negative refracting power iscomposed of a biconcave lens, and the second unit G2 with a positiverefracting power is composed of, in order from the intermediate imageside to the exit pupil EXP side, a biconvex lens, a cemented lens havinga biconcave lens and a biconvex lens arranged in this order, and abiconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 19.510 2 −17.412 6.237 1.66680 33.0 368.007 1.984 4 186.835 12.000 1.49700 81.5 5 −27.475 5.338 6 −65.1848.384 1.69895 30.1 7 6455.163 12.000 1.71999 50.2 8 −56.655 2.554 982.158 12.000 1.49700 81.5 10 −121.624 159.616 11 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 11 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Embodiment 13

FIG. 19 shows the thirteenth embodiment of the relay optical system 3according to the present invention. This embodiment is directed to therelay optical system of the sixth configuration, where, in order fromthe intermediate image side to the exit pupil EXP side, the first unitG1 with a negative refracting power is composed of a cemented lenshaving a biconcave lens and a biconvex lens, and the second unit G2 witha positive refracting power is composed of a cemented lens having abiconcave lens and a biconvex lens, and a biconvex lens.

The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 15.872 2 −23.730 5.936 1.69895 30.1 347.648 13.000 1.48749 70.2 4 −28.792 5.218 5 −123.019 7.456 1.74077 27.86 381.794 12.000 1.71300 53.9 7 −62.976 2.702 8 67.135 12.000 1.4874970.2 9 −130.910 90.018 10 INF

Regarding the spherical aberration, astigmatism and distortion of thisembodiment, aberration diagrams are shown in FIGS. 20A-20C.

Embodiment 14

FIG. 21 shows the fourteenth embodiment of the relay optical system 3according to the present invention. In this embodiment also, as inEmbodiment 13, in order from the intermediate image side to the exitpupil EXP side, the first unit G1 with a negative refracting power iscomposed of a cemented lens having a biconcave lens and a biconvex lens,and the second unit G2 with a positive refracting power is composed of acemented lens having a biconcave lens and a biconvex lens, and abiconvex lens. The numerical data of this embodiment are shown below.

Surface No. (r) R T nd νd 1 INF 19.914 2 −19.999 7.000 1.69895 30.1 347.061 14.000 1.48749 70.2 4 −27.329 5.207 5 −107.890 7.453 1.6398 34.56 178.145 12.000 1.71999 50.2 7 −72.924 2.626 8 71.985 11.997 1.4874970.2 9 −154.063 120.725 10 INF

Aberration diagrams of this embodiment are similar to those ofEmbodiment 13 and can be calculated by ray tracing using the abovenumerical data. Therefore, they are not shown.

Values regarding the above-disclosed numerical conditions in the casesof the above-described embodiments are compiled in the table below,where IM. H represents the size of the intermediate image and NArepresents the numerical aperture on the entrance side (intermediateimage side).

Emb. 1 Emb. 2 Emb. 3 Emb. 4 Emb. 5 Emb. 6 Emb. 7 f 30.000 24.994 30.00031.7042 60.3499 34.3033 71.4275 f₁ −88.077 −44.754 −240.000 −89.1616−57.2027 −46.2776 −40.1552 f₂ 31.060 25.843 33.615 26.1018 35.856825.2523 34.0467 f₁/f −2.936 −1.791 −8.000 −2.8123 −0.9479 −1.3491−0.5622 f₂/f 1.035 1.034 1.121 0.8233 0.5941 0.7361 0.4767 d_(EXP)35.930 35.587 31.053 30.1409 65.6468 38.5181 88.0016 d_(EXP)/f 1.1981.424 1.035 0.9507 1.0878 1.1229 1.2320 L 31.600 28.400 33.200 31.66332.118 28.841 33.350 L/f 1.05 1.14 1.11 1.00 0.53 0.84 0.47 IM.H 10.008.00 10.00 11.00 11.00 11.00 11.00 NA 0.04 0.04 0.04 0.04 0.04 0.04 0.04Emb. 8 Emb. 9 Emb. 10 Emb. 11 Emb. 12 Emb. 13 Emb. 14 f 48.149 54.55880.657 55.651 75.355 56.802 67.942 f₁ −63.976 −38.144 −27.812 −27.423−20.200 −94.411 −77.202 f₂ 37.458 38.815 42.251 36.328 37.630 58.30665.837 f₁/f −1.329 −0.699 −0.345 −0.493 −0.268 −1.662 −1.136 f₂/f 0.7780.711 0.524 0.653 0.499 1.026 0.969 d_(EXP) 60.042 90.020 159.930 90.029159.616 90.018 120.725 d_(Exp)/f 1.247 1.650 1.983 1.618 2.118 1.5851.777 L 43.909 51.420 53.217 60.333 60.497 58.313 60.284 L/f 0.91 0.940.66 1.08 0.80 1.03 0.89 IM.H 10.00 10.00 10.00 10.00 10.00 10.00 10.00NA 0.04 0.04 0.04 0.04 0.04 0.04 0.04

As described above, according to the present invention, it is possibleto provide a relay optical system that allows, for photographing asample image using a photographing apparatus, the photographingapparatus to be mounted on a microscope without the microscope and thephotographing apparatus excluding each other from their predeterminedpositions.

1. A relay optical system comprising, in order from an intermediateimage position toward an exit side: a first unit having a negativerefracting power; and a second unit having a positive refracting power,wherein said first unit comprises a lens that has an exit-side surfaceconcave toward the exit side, wherein said second unit comprises, inorder from the intermediate image position toward the exit side, acemented lens, a first positive lens and a second positive singlet lens,wherein said second positive singlet lens has an exit-side surfaceconvex toward the exit side, and wherein a distance from a rearmost lenssurface of said second unit to an exit pupil position is at least 30 mm.2. A relay optical system comprising, in order from an intermediateimage position toward an exit side: a first unit having a negativerefracting power; and a second unit having a positive refracting power,wherein said first unit comprises a lens that has an exit-side surfaceconcave toward the exit side, wherein said second unit comprises acemented lens, a first positive lens and a second positive lens, saidcemented lens and said first positive lens being arranged in this orderfrom the intermediate image position toward the exit side, wherein saidsecond positive lens is arranged on a side of the intermediate imageposition in reference to said cemented lens, and wherein a distance froma rearmost lens surface of said second unit to an exit pupil position isat least 30 mm.